Universal serial bus (USB) is a standard serial-communication interface for connecting a host computer (hereinafter, referred to as a host) to devices such as a printer, scanner, digital camera, large-capacity memory, and/or human interface devices (HIDs) including a keyboard, touch panel, track ball, and mouse, as just a few examples.
A USB-HUB device (hereinafter referred to as a HUB) having a single up port and a plurality of down ports is used to connect the plurality of devices having the above-mentioned USB to the host.
Referring now to FIG. 6, a block schematic diagram of a chip for HUB 61 and a chip for HID 62 is set forth.
A chip for HUB 61 includes an up port 618, a serial interface engine (SIE) 611, an end point (EP) portion 612, an HUB request processing unit 613, port control units (614 and 615) and down ports (616 and 617). Up port 618 can be for connecting devices to the host. An HUB request processing unit 613 performs a process of the HUB. The number of port control units (614 and 615) corresponds to the number of down ports (616 and 617).
Devices are connected to the host via the chip for HUB 61 by connecting the devices to the plurality of down ports (616 and 617). In the example of FIG. 6, an HID 63 is illustrated as the above-mentioned device connected to down port 617. In this example, no device is connected to down port 616.
Conventionally, a chip for HID 62 is required to be connected between the chip for HUB 61 and HID 63. A chip for HID 62 has an up port 624, a serial interface engine (SIE) 621, an end point portion 622, and a HID request processing unit 623. Up port 624 is connected to the down port 617 of the chip for HUB 61. HID request processing unit 623 performs a process of the HID 63.
As mentioned above, when a conventional USB interface is used, the connection betwer devices (e.g., HIDs) and a down ports for a HUB can include an SIE situated between to the HID request processing unit and such down ports. Because an HUB function and device functions are collected at the same address, addresses need to be given individually for the device functions. Accordingly, an SIE for identifying the address for each device function needs to be provided. Thus, as a number of HUB ports increases, circuit scale can increase. Therefore, chip size and manufacturing costs can increase.
In view of the above discussion, it would be desirable to provide a structure in which a serial interface unit (SIE) for a HUB is commonly used, so that a host may recognize a device using an SIE of a HUB.